﻿<!DOCTYPE html>
<html>
<head>
  <title>Incremental Tree</title>
  <!-- Copyright 1998-2020 by Northwoods Software Corporation. -->
  <meta name="description" content="Incrementally grow a tree as each node is expanded for the first time." />
  <meta name="viewport" content="width=device-width, initial-scale=1">

  <script src="../release/go.js"></script>
  <script src="../assets/js/goSamples.js"></script>  <!-- this is only for the GoJS Samples framework -->
  <script id="code">
    function init() {
      if (window.goSamples) goSamples();  // init for these samples -- you don't need to call this
      var $ = go.GraphObject.make;  // for conciseness in defining templates

      var blues = ['#E1F5FE', '#B3E5FC', '#81D4FA', '#4FC3F7', '#29B6F6', '#03A9F4', '#039BE5', '#0288D1', '#0277BD', '#01579B'];

      myDiagram =
        $(go.Diagram, "myDiagramDiv",  // must name or refer to the DIV HTML element
          {
            initialContentAlignment: go.Spot.Center,
            layout: $(go.ForceDirectedLayout),
            // moving and copying nodes also moves and copies their subtrees
            "commandHandler.copiesTree": true,  // for the copy command
            "commandHandler.deletesTree": true, // for the delete command
            "draggingTool.dragsTree": true,  // dragging for both move and copy
            "undoManager.isEnabled": true
          });

      // Define the Node template.
      // This uses a Spot Panel to position a button relative
      // to the ellipse surrounding the text.
      myDiagram.nodeTemplate =
        $(go.Node, "Spot",
          {
            selectionObjectName: "PANEL",
            isTreeExpanded: false,
            isTreeLeaf: false
          },
          // the node's outer shape, which will surround the text
          $(go.Panel, "Auto",
            { name: "PANEL" },
            $(go.Shape, "Circle",
              { fill: "whitesmoke", stroke: "black" },
              new go.Binding("fill", "rootdistance", function(dist) {
                dist = Math.min(blues.length - 1, dist);
                return blues[dist];
              })),
            $(go.TextBlock,
              { font: "12pt sans-serif", margin: 5 },
              new go.Binding("text", "key"))
          ),
          // the expand/collapse button, at the top-right corner
          $("TreeExpanderButton",
            {
              name: 'TREEBUTTON',
              width: 20, height: 20,
              alignment: go.Spot.TopRight,
              alignmentFocus: go.Spot.Center,
              // customize the expander behavior to
              // create children if the node has never been expanded
              click: function(e, obj) {  // OBJ is the Button
                var node = obj.part;  // get the Node containing this Button
                if (node === null) return;
                e.handled = true;
                expandNode(node);
              }
            }
          )  // end TreeExpanderButton
        );  // end Node

      // create the model with a root node data
      myDiagram.model = new go.TreeModel([
        { key: 0, color: blues[0], everExpanded: false }
      ]);


      document.getElementById('zoomToFit').addEventListener('click', function() {
        myDiagram.zoomToFit();
      });

      document.getElementById('expandAtRandom').addEventListener('click', function() {
        expandAtRandom();
      });
    }

    function expandNode(node) {
      var diagram = node.diagram;
      diagram.startTransaction("CollapseExpandTree");
      // this behavior is specific to this incrementalTree sample:
      var data = node.data;
      if (!data.everExpanded) {
        // only create children once per node
        diagram.model.setDataProperty(data, "everExpanded", true);
        var numchildren = createSubTree(data);
        if (numchildren === 0) {  // now known no children: don't need Button!
          node.findObject('TREEBUTTON').visible = false;
        }
      }
      // this behavior is generic for most expand/collapse tree buttons:
      if (node.isTreeExpanded) {
        diagram.commandHandler.collapseTree(node);
      } else {
        diagram.commandHandler.expandTree(node);
      }
      diagram.commitTransaction("CollapseExpandTree");
      myDiagram.zoomToFit();
    }

    // This dynamically creates the immediate children for a node.
    // The sample assumes that we have no idea of whether there are any children
    // for a node until we look for them the first time, which happens
    // upon the first tree-expand of a node.
    function createSubTree(parentdata) {
      var numchildren = Math.floor(Math.random() * 10);
      if (myDiagram.nodes.count <= 1) {
        numchildren += 1;  // make sure the root node has at least one child
      }
      // create several node data objects and add them to the model
      var model = myDiagram.model;
      var parent = myDiagram.findNodeForData(parentdata);

      var degrees = 1;
      var grandparent = parent.findTreeParentNode();
      while (grandparent) {
        degrees++;
        grandparent = grandparent.findTreeParentNode();
      }

      for (var i = 0; i < numchildren; i++) {
        var childdata = {
          key: model.nodeDataArray.length,
          parent: parentdata.key,
          rootdistance: degrees
        };
        // add to model.nodeDataArray and create a Node
        model.addNodeData(childdata);
        // position the new child node close to the parent
        var child = myDiagram.findNodeForData(childdata);
        child.location = parent.location;
      }
      return numchildren;
    }

    function expandAtRandom() {
      var eligibleNodes = [];
      myDiagram.nodes.each(function(n) {
        if (!n.isTreeExpanded) eligibleNodes.push(n);
      })
      var node = eligibleNodes[Math.floor(Math.random() * (eligibleNodes.length))];
      expandNode(node);
    }
  </script>
</head>
<body onload="init()">
<div id="sample">
  <div id="myDiagramDiv" style="background-color: white; border: solid 1px black; width: 100%; height: 700px"></div>
  <p><button id="zoomToFit">Zoom to Fit</button><button id="expandAtRandom">Expand random Node</button></p>
  <p>
  This diagram demonstrates the expansion of a tree where nodes are only created "on-demand",
  when the user clicks on the "expand" Button.
  As you expand the tree, it automatically performs a force-directed layout,
  which will make some room for the additional nodes.
  </p>
  <p>
  The data for each node is implemented by a JavaScript object held by the Diagram's model.
  Each node data has an <b>everExpanded</b> property that indicates whether we have already
  created all of its "child" data and added them to the model.
  The <b>everExpanded</b> property defaults to false,
  to match the initial value of <a>Node.isTreeExpanded</a> in the node template,
  which specifies that the nodes start collapsed.
  </p>
  <p>
  When the user clicks on the "expand" Button, the button click event handler finds the corresponding
  data object by going up the visual tree to find the Node via the <a>GraphObject.part</a> property
  and then getting the node data that the Node is bound to via <a>Part.data</a>.
  If <b>everExpanded</b> is false, the code creates a random number of
  child data for that node, each with a random <b>color</b> property.
  Then the button click event handler changes the value of <b>Node.isExpandedTree</b>,
  thereby expanding or collapsing the node.
  </p>
  <p>
  Some initial node expansions result in there being no children at all.
  In this case the Button is made invisible.
  </p>
  <p>
  All changes are performed within a transaction.
  You should always surround your code with calls to <a>Model.startTransaction</a> and <a>Model.commitTransaction</a>,
  or the same methods on <a>Diagram</a>.
  </p>
  <p>
  The diagram's <a>Diagram.layout</a> is an instance of <a>ForceDirectedLayout</a>.
  The standard conditions under which the layout will be performed include
  when nodes or links or group-memberships are added or removed from the model,
  or when they change visibility.
  In this case that means that when the user expands or collapses a node,
  another force-directed layout occurs again, even upon repeated expansions or collapses.
  </p>
</div>
</body>
</html>
